Vacuum tube



Patented Nov.- 22, 1932 UNITED STATES PATENT OFFICE LEO Il- BECK, 0F JACKSON HEIGHTS, NEW YORK, ASSIGN'OR T0 CLAUDE NEON LIGHTS, INC., 013 NEW YORK, N. Y., CORPORATION OF NEW YORK VACUUM TUBE No Drawing.

This invention relates to positive column or gaseous conductor tubes of the kind in which a column of more or less rarefied gas is caused to glow and radiate light dueto the ionization of. the gas by the passage of a high potential alternating current therethrough.

Positive column tubes have heretofore been proposed in which the rarefied atmosphere within the tube is composed of one of that group of gases known as the rare gases, such as neon, argon, helium, Xenon, or krypton. Each of these gases emits a light of a characteristic color when caused to vibrateby the passage of an electric current. For instance, neon, when caused to glow, emits an orange red color; argon emits a violet color; and helium emits a yellowish color.

It has also been proposed to obtain a blue color from a positive column tube by the inclusion of mercury vapor therein. In this instance, the rare gas, such as neon, serves as the path for the ions travelling toward'the cathode and is preferred because of its low voltage gradient which contributes to long life of the tube, primarily because it contributes to long life of the electrode. Such a tube is relatively cool but under moderate temperatures the ionization of the gaseous column is suificient to maintain the mercury in a vaporized condition so that it is distributed throughout the tube and the color which it emits upon ionization predominates. This color is blue and masks the orange red of the vibrating neon.

While neon is a very eflicient gas, because of its low voltage gradient, it has the disadvantage that it does not develop enough heat to maintain the mercury vaporized at low temperatures and the tube, in cold weather is likely to assume a striated appearance. 1n which strlae of an orange red color ap-' pear, that being the characteristic color of neon. This striation is due to the separation or condensation of mercury at those points so that only the neon color appears and also to the capillary flect of neon, that is, its tendency to separate readily from other constituents, wherever the difference in atomic weight between the two is great. Of course,

mercury, whereof the atomic weight varies Application filed December 19, 1927. Serial No. 241,277.

greatly from neon contributes to the ready separation of the neon therefrom.

The primary object of the present invention is a positive column tube emitting light of a blue color which will retain its color despite the low temperatures to which it is subjected in cold weather so that the tube may be applicable, for instance, in advertising sign lighting; beacons and other types of illuminations.

This is realized broadly by a tube whereof the contents comprises a gas which, upon ionization, will emit light of a color which shall serve as a background color, that is,

one that is nearer the blue than the red of the spectrum and thus tend to blend with the color emitted by the ionized mercury vapor. Preferably, the tube light shall also contain a gas having a high voltage gradient to supply heat to the tube to oifset the low temperature in which the tube may be operating and keep the mercury vaporized It has been found that the several gases of the rare gas group possess advantages and disadvantages from the standpoint of positive column tube illumination where a blue light is desired as emitted by vibrating mercury vapor.

Argon possesses the advantage that it is the heaviest of the group and therefore carries mercury vapor the easiest and, having a low heat conductivity, tends to keep the heat ation in the color of the tube from the prescribed blue will not be particularly noticeable. On the other hand, argon has the disadvantage that it runs very cool and there- This is a color which is the fore not enough heat is developed to maintain the mercury vaporized at low temperatures.

Helium, upon ionization in a positive column tube, develops considerable heat, and for this reason may be relied upon to keep the mercury vaporized. The disadvantage of helium, however, is that it is a very ineflicient gas because of its high volta e gradient.

Neon has the advantage t at it is a very eflicient gas that is, it has a low voltage gradient, and hence has less deleterious effect on the electrodes of the tube. On the other hand, neon is not as effective in maintaining the mercury vaporized in cold weather, as some of the other gases of the group because the ionized neon does not develop a large quantit of heat. Also because of the capillary e ect of neon, a mixture of neon and mercu will more easily separate and give the striated efiect noticed in cold weather with positive column tubes containing neon and mercury. This striation takes the form of bands of the characteristic neon color or nearly so appearing in the otherwise blue tube resulting from theinclusion of the mercury therein. This tendency to separate is due to the fact that a mixture containing a gas whereof the atomic weight difi'ers materially from the atomic weig.-t of mercury is not as stable at lower temperatures, as a mixture of gases and/or vapors whereof the atomic weights are more nearly equal.

In carrym out the invention, therefore, a mixture 0% the various gases, with the requisite amount of mercury vapor, is selected which shall ermit the advantageous properties of the di erent gases to be utilized while the disadvantageous features are notpronounced or are overcome by certain properties of other gases of the mixture. Thus, suflicient argon is taken to give a background color to the ionized mixture, should the mercury condense, which color closel approximates the desired blue color. g suflicient rpliantity of ar on is also availed of to carry t e mercury, that is, by reason of the capillary efl'ect, so that there shall be no separation of mercury vapor from the gases of the mixture at the temperature to which the tube li ht may be selected. Sufficient helium is a (led to the mixture so that, upon ionization, enough heat will be developed to maintain the mercu? vaporized at the selected temperatures. he quantities of argon and helium so selected will not be suflicient to 'maintain the tube contents at that pressure which experience has demonstrated is the most eflicient pressure for the operation of the tube light. l

It may be assumed by way of example that ar on, sufiicient in amount is put into the so that the pressure is equal to two millimeters of mercu and that five millimeters of helium are ad ed. This mixture would give the results sought so far as colored, the

ackground color of argon and stability, is concerned but the tube contents would be mostl helium. Tube electrodes splutter readi y in an atmosphere of helium as well as atv such pressure. To overcome'these disadvantages, the pressure of the tube is raised to that most conducive to long life of the electrodes, say fifteen millimeters, by the addition of a diluent such as neon in an amount of about eight millimeters. Thus the increased pressure not only prevents electrode spluttering but the electrodes splutter least in an atmosphere of neon because of its low voltage gradient.

It will thus be seen that the temperature of the positive column tube is controlled and prevented from falling below a temperature at which the mercury Will remain vaporizedby means of the selection of gases within the tube. When the lowest temperature at which the tube light is to be run is determined, the relative proportions of the two or more gases to comprise the mixture may be selected. For instance, a tube light containing neon and helium in the proportion of 30% neon and helium with the necessary amount of mercury and argon in an amount equivalent to a pressure of half millimeter, will maintain its blue color down to a temperature of minus )28 F. When the pressure of the rare gases of the tube contents is 7 millimeters. The change may be delayed until the temperature falls to -4 1 F. by increasing the total pressure of the rare gases in the a tube to fifteen millimeters, and to 49 F. by increasing the pressure of the rare gases in the tube to thirty millimeters.

As an example the tube contents may comprise neon and helium in the proportion of 30% neon and 70% helium, argon in an amount equivalent to a pressure of one-half millimeter and the usual amount of mercury, (for example from 3 to 4 grams per 15 feet of tubing) so that the total pressure of the rare gases in the tube amounts to fifteen millimeters. This mixture will maintain the desired blue color until the temperature falls to about 41 F. If the proportions of the above are varied to include two millimeters of argon the tube will not change color until a temperature of -47 F. is reached.

It will thus be seen that a positive column tube emitting a blue color is maintained at very low temperatures, much lower than would be possible by the use of a single gas with mercury and that by a selection of the number and quantity of the gases the temperature at which the tube will lose its blue color may be controlled.

Various modifications will occur to those 120 skilled in the art in the composition, proportion and pressure of the gases contained within the positive column tube in conjunction with mercury and no limitation'is intended by the phraseology or proportions except as set forth in the appended claims.

What I claim is:

1. In a positive column tube, a gas adapted to maintain substantially its color at 1111 usual temperatures, comprising a color'affording material, a background color sup- I plying gas and a heatsupplying gas.

I 2. In a positive column tube, a gas adapted to maintain substantially its color at unusual temperatures comprising an ingredient whereof the vapor emits colored light upon ionization, a background color supplying gas and a heat supplying gas.

3. In a positive column tube, a gas adapted to maintain substantially its color at low temperatures comprising mercury, a background supplying rare gas, and a heat supplying rare gas.

4. In a positive column tube, a as adapted to maintain substantially its mfior at low temperatures comprising mercury, a rare gas having low thermal conductivity and a rare gas having a high voltage gradient.

5. In a positive column tube, a gas adapt ed to maintain substantially a blue color at low temperatures comprising mercury, a rare gas having low thermal conductivity, a rare gas having a high voltage gradient and a rare gas as a dilutant.

6. In a positive column tube, a gas adapted to maintain substantially a blue color at low temperatures comprising mercury, a rare gas having low thermal conductivity, a rare gas having a highvoltage gradient, and means to increase the pressure of the tube contents.

7. In a positive column tube, a gas adapted to maintain substantially its color at low temperatures comprising mercury, a background supplying rare gas, a'heat supplying rare gas, and neon.

8. In a positive column tube, a gas adapted to maintain substantially its color at low temperatures comprising mercury, a rare gas having low thermal conductivity, arare gas havirig a high voltage gradient, and neon.

9. n a positive column tube, a gas adapted to maintain substantially a blue color at low 1 supplying a back ground color and temperatures comprising mercury, a rare gas helium. 10. Ina positive column tube, a gas adapted to maintain substantially a blue color at low temperatures comprising mercury, argon and a heat supplying rare gas.

11. In a positive column tube, a gas adapted to maintain substantially a blue color at low temperatures comprising mercury, a rare gas supplying a background color, helium and neon.

12. In a positive column tube, a gas adapted to maintain substantially a blue color at low temperatures comprising mercury, argon, a heat supplying rare gas, and neon.

13. In a positive column tube, ed to maintain substantially a blue color at low temperatures comprising mercury, argon, helium and a rare gas as a dilutant.

14. In a positive column tube, a gas adapted to maintain substantially a blue color at low temperatures helium and neon.

15. In a positive column tube, a gaseous mixture adapted 'to maintain its blue color at low temperatures comprising mercury, neon and hehum in an amout equal to 13 millimeters pressure and in the proportion of 30% neon and helium and argon in an amount equal to two millimeters pressure.

16. A positive column tube adapted to emit a desired color at low temperatures, the tube contents com rising one 'or more color emitting vapors, elium and argon.

1 A positive column tube adapted to emit a desired color at low temperatures, the tube contents comprising one or more color emitting vapors, a rare gas having a high voltage gradient, a rare gas having a low voltage gradient, and neon. 1 e

18. In a positive column tube a gas adapted to maintain substantially a blue color at low temperatures comprising mercury, a rare gas having low thermal conductivity, a rare gas having a high voltage gradient, and .a rare gas to increase the pressure of the tubecontents.

19. A luminescent gas discharge tube containin mercury, argon and helium, the per cent 0% helium being greater than 50 per cent of the rare gas content, the tube being adaptcomprising mercury, argon,

ed to maintain its blue color at low temperatures.

20. A luminescent gas discharge tube containing mercury, argon, neon and helium, the per cent of helium being greater than 50 er cent of the rare gas content, the tube being adapted to maintain its blue color at low temperatures.

In testimony whereof I aflix my signature.

LEO L. BECK.

a gas adapt- 

